The present invention relates to a liquid crystal display device, which is capable of controlling any change in molecular orientation by electric fields having different directions and strengths so as to achieve fast response of an electric field, of liquid crystal display devices in which an electric field alters a molecular orientation of liquid crystal having dielectric anisotropy, and further concerns a displaying method thereof.
As shown in FIGS. 12 and 13, a liquid crystal display device is formed by bonding a pair of substrates 101 and 102 together such that surfaces having the electrodes 103 and 104 oppose each other. FIG. 14 shows a sectional view of the device, in which insulating films 107 and 108 and orientation films 109 and 110 are stacked if necessary on electrodes 103 and 104 between a pair of substrates 101 and 102, and if necessary, an orientating operation such as rubbing is performed on the orientation films. Spacers 111, each having a desired diameter, are disposed on the substrate so as to bond the substrates together with an even gap. The substrates are fixed with a sealing agent 112. Finally, liquid crystal 113 is filled from an opening formed on the sealing agent, and the opening is sealed so as to complete the device. An orientating operation performed on the orientation films can achieve even orientation.
Each of the electrodes externally includes an extended part so as to apply an electric field having an arbitrary signal waveform to the liquid crystal. The liquid crystal alters its orientation according to an applied electric field and polarizes and modulates light passing through liquid crystal. A polarizer for visualizing polarization and modulation is provided if necessary so as to obtain a function of a display device. To transmit light through the liquid crystal layer, at least one of the electrodes needs to be a transparent electrode made of material such as ITO (indium tin oxide).
Further, liquid crystal display devices are broadly categorized into two kinds in view of an electrode structure. The following methods are available: a direct matrix method of forming stripe electrodes intersecting with one another, and an active-matrix method (see FIG. 13) of forming signal electrodes 105 intersecting on another on one of the substrates and forming switching elements 106 such as a transistor. In many cases, nematic liquid crystal is currently used as a liquid crystal material for any one of the methods.
The direct matrix method is simple in construction and manufacturing; however, a switching element is not provided for each pixel, so that all the pixels are coupled to one another with a capacitance. Thus, so-called crosstalk may appear, in which a switching threshold value becomes less clear in each of the pixel and a displayed image becomes less sharp with increasing number of pixels. Moreover, a transparent electrode such as ITO is a conductive material but is 100 to 1000 times higher than metal, etc. in resistance value. Thus, deformation on a signal waveform becomes more serious due to an electrode resistance of a transparent electrode, in response to the needs for a larger display device and a larger display capacity.
According to Japanese Unexamined Patent Application No. 287671/1995 (Tokukaihei 9-127494), a transparent electrode and a metallic wire are disposed in parallel so as to reduce an electrode resistance; however, a smaller aperture ratio lowers a luminance and reduces simplicity in manufacturing, that has been a characteristic of a direct matrix method.
Meanwhile, in the active-matrix method, a switching element is formed for each pixel, so that the manufacturing is more difficult than the direct matrix method. However, the pixels can be separately driven, so that no crosstalk occurs and a considerably clear image can be displayed. Also, it is possible to form a signal line making no contribution to transmission of light by using a metal such as Ti and Al. An opposing transparent electrode has a flat shape requiring no patterning, so that an electrode resistance hardly causes deformation on a signal waveform. Consequently, it is relatively easy to respond to a larger display device and a larger display capacity.
Therefore, a simple construction of the direct matrix method and a characteristic of a ferroelectric liquid crystal have been used in an attempt to solve crosstalk (N. Itoh et. al, Proceedings of The Fifth International Display Workshops (IDW""98), (1998) p. 205, xe2x80x9817xe2x80x9d Video-Rate Full Color FLCD""). Ferroelectric liquid crystal is characterized by a property of memory and xcexcs-digit fast response (N. Clark et. al, xe2x80x9cApply. Phys. Lett., 36xe2x80x9d (1980), p.899 xe2x80x9cSubmicrosecond bistable electro-optic switching in liquid crystalsxe2x80x9d), so that displayed information can be successively written at a high speed for each scanning line and the written information can be maintained until a rewriting signal is inputted without applying voltage. Thus, it is possible to adopt a line-sequential driving method. With this arrangement, the direct matrix method can display a clear image as the active-matrix method, without causing crosstalk.
However, in the case of the direct matrix method, a problem of an electrode resistance cannot be solved by ferroelectric liquid crystal. An electrode resistance adversely affects a speed of a signal waveform as well as deformation thereof. Particularly in the case of a ferroelectric liquid crystal characterized by fast response, the foregoing technique of disposing a transparent electrode and a metallic wire in parallel is necessary. Consequently, a luminance is reduced by a smaller aperture ratio and a simple manufacturing cannot be achieved. Further, an electrode resistance increases power consumption and causes heat on a panel.
Considering this point, except for some of low-grade display devices, the active-matrix method is more suitable to a liquid crystal display device for displaying a moving picture with high resolution. Particularly, a thin-film transistor (TFT) method using a three-terminal element is superior to other methods such as a metal insulating film metallic layer (MIM) method using two-terminal element.
In order to allow a liquid crystal display device to contend with a CRT, which has been currently used as a main display device, and to replace the CRT as a flat display device in the future, some problems on picture quality need to be solved. The most critical problem of liquid crystal is a slow response to a signal waveform electric field. Here, the following describes the relationship between response speed and picture quality of liquid crystal.
On a currently used TFT-nematic liquid crystal display device (hereinafter, abbreviated as LCD), a moving image may be recognized as a blurred image. The cause is fully discussed in xe2x80x9cKurita, under the sponsorship of a LCD forum, xe2x80x9cFor LCD Advancement to CRT monitor market, -from the viewpoint of moving image display-xe2x80x9d, section 1 xe2x80x9cdisplaying method of a hold type display and picture quality of a moving picture display, Liquid Crystal Society, 1998xe2x80x9d.
CRT and LCD differ in time response of displayed light. As shown in FIGS. 15 and 16, CRT has a displayed light of impulse type (FIG. 15), and LCD has a displayed light of hold type (FIG. 16). This is because liquid crystal only acts as a shutter for transmitting and shielding backlight, not spontaneous light, and because TN liquid crystal, which has been known and widely used, has a response speed of about 15 ms so as to make response by fully using one field of 16.7 ms. Hereinafter, for convenience of explanation, response time is equal to response speed in meaning.
In such a hold-type display, of eyeball movements, when a tracking movement (right and left eyeballs smoothly track a moving object substantially in the same manner), which is the most important for perceiving a moving image, and visual time integral effect are obtained in a substantially complete manner, the observer perceives an average brightness of some pixels. Thus, an image to be displayed by different pixels is completely erased. A ratio of the tracking movement is reduced in an eyeball movement with an increase in a moving speed; however, movement within 4 to 5 (degree/second) can be sufficiently followed only by the tracking movement. Further, regarding a short time period, a maximum speed of the tracking movement is 30 (degree/second). With respect to time integral effect, light stimulus in a short time of within several tens ms is integrated in a substantially complete manner if a luminance is at a certain degree or less.
A large number of actually displayed moving images satisfy the above angular speed and luminance, so that a blurred moving image appears due to a so-called eye tracking on a hold-type display. In order to eliminate a blurred moving image on LCD, it is necessary to adopt an impulse-type display used in CRT. Instead of providing backlight all the time, it is possible to adopt a method of using a shutter to provide an apparent impulse emission and a method of providing fast flashing. In any case, a response speed of liquid crystal needs to be remarkably higher than a current speed.
Referring to FIG. 17, the following describes this point. In FIG. 17, a horizontal axis indicates time and a vertical axis indicates a quantity of emitted backlight and a quantity of transmitting light on LCD. In FIG. 17, t represents time required for opening a gate (gate ON time), which is a scanning signal line of TFT. n represents the number of scanning signal lines (gate line). Hence, a display device having n scanning lines requires time of txc3x97n to turn on all the TFTs. A curve of FIG. 17 indicates a time response property of liquid crystal, and xcfx84r indicates a rising response speed of liquid crystal.
After the last gate line of the n gate lines is turned on and liquid crystal on the nth line responds, a backlight is lit or emitted so as to provide an impulse-type display in the same manner as CRT. According to the foregoing document, backlight effectively used for an impulse-type display has an emitting period ratio (compaction ratio) of 25% for one field of 16.7 ms. Thus, T needs to be set at about 4 ms. When reproducing high-definition broadcasting having 1025 scanning lines, n is set at about 1000. A response speed of liquid crystal is xcfx84r=16.7 msxe2x88x92txc3x97nxe2x88x92T. Thus, the following relationship needs to be satisfied: xcfx84rxe2x89xa616.7 msxe2x88x924 msxe2x88x92txc3x97n.
Currently, regarding amorphous silicon (xcex1Si)xe2x80x94TFT achieving a large display device of 20 inch, a gate-on time t of TFT is about 10 xcexcs. Regarding polysilicon (PSi)xe2x80x94TFT, which hardly provides a large display but has a high mobility of electrons, a gate-on time t is about 3 xcexcs. It is understood that a response speed needs to be 2.7 ms or less in the case of (xcex1Si)xe2x80x94TFT and at 9.7 ms or less in the case of (PSi)xe2x80x94TFT, in order to realize a full-spec moving image having no blurred image.
A PSixe2x80x94TFT has a high process temperature of 1000xc2x0 C. or more, so that quartz glass needs to be used instead of a normal glass substrate. Thus, it is difficult to achieve a large display and to realize a display device for providing full-spec high-definition broadcasting.
In FIG. 18, liquid crystal returns to an original state in different fields and transmitted light is shielded. xcfx84d represents a falling response speed, which requires fast response as a rising response speed xcfx84r. As earlier mentioned about the rising response, conventional TN liquid crystal has a response speed of about 15 ms. Even if the backlight system is replaced with an impulse type, it is not possible to achieve a full-spec moving image having no blurred image by using xcex1Sixe2x80x94TFT at a response speed of 2.5 ms or less. Falling response is further slow from several tens ms to 100 ms.
Additionally, the following discusses the reason why the current liquid crystal has a low response speed. FIGS. 19(a) and 19(b) show electric field response of nematic liquid crystal. Transition time from FIG. 19(a) to FIG. 19(b) is rising time xcfx84r. Transition time from FIG. 19(b) to FIG. 19(a) is falling time xcfx84d. A cylinder indicates a liquid crystal molecular 114. The nematic liquid crystal is switched according to a dielectric anisotropy xcex94∈, which is a permittivity difference between a molecular major axis direction and a molecular minor axis direction, and torque is produced by dielectric energy of (xc2xd)xcex94∈E2 that occurs between liquid crystal and an applied electric field E115, so that orientation is changed. When xcex94∈ is positive, orientation is changed such that a molecular major axis conforms to an electric field. When xcex94∈ is negative, orientation is changed such that a molecular major axis intersects with an electric field.
Dielectric energy of (xc2xd)xcex94∈E2 is scalar which does not depend upon a direction of the electric field E115; thus, even when the electric field E is ac, the nematic liquid crystal is changed only in one direction. After removing the electric field, the state returns to original orientation due to a reduction in viscosity of the liquid crystal. Hence, falling (xcfx84d) after removing an electric field is generally slower than rising (xcfx84r) caused by applying an electric field.
FIGS. 20(a) and 20(b) show electric field response of ferroelectric liquid crystal. Transition time from FIG. 20 (a) to FIG. 20(b) is rising time xcfx84r. Transition time from FIG. 20(b) to FIG. 20(a) is falling time xcfx84d. The ferroelectric liquid crystal is switched according to Psxc2x7E, which is inner product energy of a spontaneous polarization Ps 116 and the electric field E115, and a direction of the spontaneous polarization Ps corresponds to an electric field direction so as to perform so-called in-plane switching, which is a switching in parallel on a surface of the substrate. Inner product energy Psxc2x7E of the spontaneous polarization PS and the electric field E is vector quantity which depends upon a direction of the electric field E, so that a direction of the electric field E can switch optical rising (xcfx84r) and falling (xcfx84d) at a high speed.
As described above, ferroelectric liquid crystal is considerably advantageous in view of response speed; however, many problems peculiar to the ferroelectric liquid crystal arise. Nematic liquid crystal is free from these problems. Ferroelectric liquid crystal is smectic liquid crystal, which is closer to crystal as compared with nematic liquid crystal and has a layer structure in its molecular array. Thus, it is difficult to evenly orient a large area. Besides, the layer structure is prone to damage and the orientation may become uneven by mechanical impact, so that reliability may be reduced. To secure impact resistance, a wall-shaped structure can be formed in a display device so as to firmly fix a substrate (N. Ito et al., xe2x80x9cProceedings of The Fifth International Display Workshops (1998) p.205 xe2x80x9817xe2x80x9d Video-Rate Full Color FLCDxe2x80x9d); however, orientation becomes more difficult by forming a wall.
Further, ferroelectric liquid crystal has a spontaneous polarization, which is kept in one direction if switching is not carried out while a display signal is inputted. If this state continues for a long time, electrical charge may be accumulated at an interface between ferroelectric liquid crystal and an orientation film, resulting burn on a screen.
Moreover, ferroelectric liquid crystal needs to have a thin cell structure of 2 to 1.5 xcexcm to make use of its characteristics. Hence, a cell capacity is larger than normal nematic liquid crystal (cell thickness of about 4 xcexcm), causing a reduction in quantity of charging from TFT to a pixel within required time. Consequently, insufficient switching may occur. In order to solve this problem, the charging ability of TFT needs to be improved; however, a considerable change in a structure of TFT is not preferable in cost because the manufacturing becomes more difficult.
Therefore, studies have been conducted in earnest to improve response speed of nematic liquid crystal, which has been conventionally used. Actually, studies have been conducted to improve response speed by using orientation other than TN orientation, which has been mainly used and known well.
For example, a study has been known to achieve fast response of nematic liquid crystal by using orientation called bend cell or pie cell (T. Miyashita et al., xe2x80x9cConference Proceedings of The 13th International Display Research Conference (Euro Displayxe2x80x9893)xe2x80x9d, (1993) p.149). It has been reported that a bend orientation cell shortens rising response speed to about 2 ms as compared with about 15 ms of the conventional TN orientation cell. The fast response is achieved by controlling a flow produced by response of liquid crystal (Miyashita et al., under the sponsorship of a LCD forum, xe2x80x9cFor LCD Advancement to CRT monitor market, -from the viewpoint of moving image display-xe2x80x9d, section 7 xe2x80x9cField Sequential full-color liquid crystal display using a fast response of OCB liquid crystalxe2x80x9d).
This flow is considerably large in twisted orientation such as TN orientation, resulting in slow response. The rising response speed may be increased in the same manner as bend cell only by switching between vertical orientation and horizontal orientation. However, these methods for reducing a flow also use dielectric anisotropy in the same manner as the conventional nematic liquid crystal. Thus, rising response speed is high upon application of an electric field; however, falling upon removing an electric field is slow as the conventional liquid crystal.
Therefore, some methods of solving slow falling response by a device structure have been reported in xe2x80x98D. J. Channin et al., Applied Physics Letters, Vol.28, (1976) p.300 xe2x80x9cRapid Turn-off in triode optical gate liquid crystal devicesxe2x80x9cxe2x80x99 and xe2x80x98Shiotsu et al., xe2x80x9cBasic Study of Liquid Crystal Light Bulb using a Comb Electrodexe2x80x9d, Society for Electronic Information Communication Shinetsu Branch Meeting, 1987xe2x80x99.
For instance, a plural gate structure has been proposed. Instead of parallel opposing electrodes arranged in a simple manner, a plurality of electrodes are three-dimensionally disposed, and electric fields with different directions are applied to nematic liquid crystal so as to switch an orientation direction according to an electric field direction. Changes in orientation are all controlled by an electric field; thus, fast response as the conventional rising can be achieved both at optical rising and falling, unlike the conventional falling due to a reduction in viscosity.
Techniques for three-dimensionally disposing electrodes are disclosed in Japanese Unexamined Patent Application No. 222397/1994 (Tokukaihei 6-222397) and Japanese Unexamined Patent Application No. 258245/1997 (Tokukaihei 9-258245). These techniques only relate to so-called in-plane switching (hereinafter, abbreviated as IPS) for switching nematic liquid crystal in parallel on a substrate. IPS is effective for widening a viewing angle of a liquid crystal display device; however, a direction of an applied electric field cannot be changed and switching is carried out by applying and removing an electric field. Thus, these techniques are equal to the conventional art in response speed.
FIGS. 21(a) and 21(b) schematically show the method of xe2x80x9cApplied Physics Letters, Vol.28, (1976) p.300xe2x80x9d. FIGS. 22(a) and 22(b) schematically show the method of xe2x80x98Shiotsu et al., xe2x80x9cBasic Study of Liquid Crystal Light Bulb using a Comb Electrodexe2x80x9d, Society for Electronic Information Communication, Shinetsu Branch Meeting, 1987xe2x80x99. Substrates, an orientation film, and the like are omitted in the figures.
In FIGS. 21(a) and 21(b), an electrode 118 and an electrode 119 are disposed on one of the substrates while a resistant thin film 120 is sandwiched therebetween, and an opposing electrode 117 is disposed on the other substrate. According to the above document, the resistant thin film 120 has a sheet resistor of 107 to 109 xcexa9/xe2x96xa1 and is formed by depositing amorphous Si or carbon film with a thickness of about 100 xc3x85. As shown in FIG. 21(a), when the electrode 118 and the electrode 119 are set at a ground level, the resistant thin film is also set at the same ground level. When signal voltage Vc is applied to the opposing electrode 117, an electric field 115 appears across the pixel in an arrow direction perpendicular to the substrate and a liquid crystal molecule is oriented perpendicularly to the substrate. In this case, dielectric anisotropy of the liquid crystal is positive.
As shown in FIG. 21(b), when signal voltage Vd is applied to the electrode 118 so as to set the electrode 119 and the opposing electrode 117 at a ground level, an electric field 121 appears between the electrodes 118 and 119 horizontally to the substrate, and a liquid crystal molecule between the electrodes 118 and 119 is oriented horizontally to the substrate. Molecular orientation can be controlled by an electric field both at optical rising xcfx84r and falling xcfx84d; thus, unlike the conventional art, it is possible to solve slow falling caused by a reduction in viscosity. In FIGS. 22(a) and 22(b), an electrode 122 and an electrode 123 are disposed on one of substrates while a resistant thin film 120 is sandwiched therebetween, and an electrode 124 and an electrode 125 are disposed on the other substrate while a resistant thin film 120 is sandwiched therebetween. In FIG. 22(a), electrical signals with equal polarities are applied to the electrodes 122 and 123, and signals with opposite polarities are applied to the electrodes 124 and 125, so that the resistant thin films are equal in voltage level respectively to the electrodes 122 and 123, and the electrodes 124 and 125. And then, the electric field 115 appears across a pixel in an arrow direction perpendicular to the substrate, and a liquid crystal molecule is oriented perpendicularly to the substrate. Dielectric anisotropy of the liquid crystal is positive.
In FIG. 22(b), electrical signals with opposite polarities are applied to the electrodes 122 and 125, and the electrodes 123 and 124 are set at a ground level; thus, a diagonal electric field 126 appears between the electrode 122 and the electrode 125, and a liquid crystal molecule is oriented diagonally to the substrate. Molecular orientation can be controlled by an electric field both at optical rising xcfx84r and falling xcfx84d; thus, unlike the conventional art, it is possible to solve slow falling caused by a reduction in viscosity.
As described above, the plural gate structure can solve slow falling response but has a major problem on practical use as follows: a plurality of switching elements are required for one pixel as shown in FIGS. 21(a) to 22(b). In FIGS. 21(a) and 21(b), the electrode 117 and the electrode 118 need to be switched, so that two switching elements are necessary. In FIGS. 22(a) and 22(b), the electrodes 122 and 125 successively receive constant electrical signals; however, the electrodes 123 and 124 require the repetition of applying and suspending a signal, so that two switching elements are necessary.
Namely, it is necessary to form the switching elements on both of the substrates, so that manufacturing cost is doubled as compared with a conventional active-matrix display device. Further, considering a yield of the switching element, the more elements provided, the more defects occur. Consequently, the structure has a serious disadvantage in cost.
Additionally, a liquid crystal display device currently uses a color filter for providing a color display. However, a color filter pigment is less resistant to a high temperature, gas, acid, etc., so that a TFT is directly formed on a glass substrate and the color filter is disposed on an opposing substrate. It is not practical to form switching elements on both substrates because conventionally it has been too difficult to form a TFT on a color filter.
The second problem is the resistant thin film. As described above, the resistant thin film is made of a material such as Si and carbon with an extremely small thickness of about 100 xc3x85. It is quite difficult to evenly form such a thin film on a large area in a technical point of view. In order to form an even film by deposition on a large area, a film thickness needs to be 500 xc3x85 or more, preferably about 1000 xc3x85. For example, regarding FIGS. 21(a) and 21(b), the electrodes 118 and 119 of FIG. 21(a) are electrically connected to each other so as to generate an electric field on a pixel therebetween; meanwhile, in FIG. 21(b), the thin film needs to be a conductive material with high resistance to prevent current from being applied between the electrodes 118 and 119 due to opposite polarity signals applied to the electrodes. In an actual arrangement, high resistance deforms a waveform applied to a pixel between the electrodes 118 and 119, so that an electric field with sufficient strength cannot be applied. Besides, although a thin film is closer to a transparent film, a problem in luminance arises by stacking a material such as Si or carbon on a pixel because the material does not transmit light.
The objective of the present invention is to provide a liquid crystal display device which can achieve fast response and even display without a blurred moving image, and to provide a displaying method thereof.
In order to attain the above objective and to provide a liquid crystal display device which can suppress an increase in manufacturing cost while improving picture quality with fast response, the liquid crystal display device of the present invention, in which liquid crystal is formed in a gap between a pair of substrates including at least a single light-transmitting substrate, the device having a construction in which an electrode is formed on the substrate to apply a signal waveform electric field from outside to the liquid crystal, the liquid crystal changes its orientation according to an applied signal waveform, emitted light is modulated, and the modulation is visualized, is characterized in that a first substrate of the paired substrates includes a switching element and a switching electrode connected to the switching element, and a second substrate includes an opposing electrode and an insulation film formed on the opposing electrode, and a plurality of sub electrodes on the insulation film.
According to the above arrangement, of the paired substrates, the first substrate includes the switching element and the switching electrode connected to the switching element, and the second substrate includes the opposing electrode, the insulation film formed on the opposing electrode, and a plurality of the sub electrodes formed on the insulation film.
Additionally, the following construction is also applicable: a first substrate of the paired substrates includes a switching electrode where an image signal is applied, and a second substrate opposing the first substrate includes an opposing electrode where an image signal is not applied, an insulation film formed on the opposing electrode, and a plurality of sub electrodes where an image signal is not applied, the sub electrodes being formed on the insulation film.
Therefore, when an image signal is applied via the switching element to the electrode (switching electrode) connected to the switching element, the switching electrode has a predetermined potential. In this case, a direction of an electric field, which is applied to liquid crystal, is varied between parallel and perpendicular to the substrate, depending upon whether a potential of the switching electrode is in phase or in opposite phase with a potential of the electrode (sub electrode), which is not connected to the switching electrode. Thus, the orientation of liquid crystal varies between horizontal orientation and vertical orientation. Consequently, the orientation of liquid crystal is varied by changing a potential phase of the switching electrode.
As a result, rising response and falling response can be controlled by an electric field. A reduction in viscosity causes no falling response, so that fast response can be achieved.
Therefore, fast response is available without a blurred moving image.
Further, the present invention does not need to form a resistant thin film, which is difficult to evenly form because of its small thickness. Hence, it is possible to prevent uneven display.
Moreover, the present invention requires only a single element for switching. Thus, it is possible to suppress an increase in manufacturing cost.
Besides, nematic liquid crystal is applicable to the present invention. Namely, without the necessity for ferroelectric liquid crystal, which achieves fast response but causes a peculiar problem such as uneven orientation, low resistance to impact, and burn, it is possible to achieve fast response by using nematic liquid crystal, which has been widely used, relatively easy to handle, and less prone to the above problems. For this reason, the problems of even orientation, resistance to impact, and burn do not occur. Consequently, with nematic liquid crystal, it is possible to provide a liquid crystal display device making high-speed electric field response at optical rising and falling.
Also, a displaying method of the liquid crystal display device according to the present invention is characterized in that different constant electric signals are respectively inputted to the opposing electrode and the sub electrode, and an electric signal varying according to an image signal is inputted to the switching element, in the liquid crystal display device having the above construction.
According to the above arrangement, different constant electric signals are inputted respectively to the opposing electrode and the sub electrode, and an electric signal varying according to an image signal is inputted to the switching element.
Here, the following construction is also available: constant electric signals having different voltage values are inputted to the opposing electrode and the sub electrode, and an electric signal varying according to an image signal is inputted to the switching electrode.
Hence, when an image signal is applied via the switching element to the electrode (switching electrode) connected to the switching element, the switching electrode has a predetermined potential. In this case, a direction of an electric field, which is applied to liquid crystal, is varied between parallel and perpendicular to the substrate, depending upon whether a potential of the switching electrode is in phase or in opposite phase with a potential of the electrode (sub electrode), which is not connected to the switching electrode. Thus, the orientation of liquid crystal varies between horizontal orientation and vertical orientation. Consequently, the orientation of liquid crystal is varied by changing a potential phase of the switching electrode.
As a result, rising response and falling response can be controlled by an electric field. A reduction in viscosity causes no falling response, so that fast response can be achieved.
Therefore, fast response is available without a blurred moving image.
Further, the present invention does not need to form a resistant thin film, which is difficult to evenly form because of its small thickness. Hence, it is possible to prevent uneven display.
Moreover, the present invention requires only a single element for switching. Thus, it is possible to suppress an increase in manufacturing cost.
Besides, nematic liquid crystal is applicable to the present invention. Namely, without the necessity for ferroelectric liquid crystal, which achieves fast response but causes a peculiar problem such as uneven orientation, low resistance to impact, and burn, it is possible to achieve fast response by using nematic liquid crystal, which has been widely used, relatively easy to handle, and less prone to the above problems. For this reason, problems of even orientation, resistance to impact, and burn do not occur. Consequently, with nematic liquid crystal, it is possible to provide a liquid crystal display device making high-speed electric field response at optical rising and falling.
Furthermore, the displaying method of the liquid crystal display device according to the present invention is characterized in that the opposing electrode is grounded, in-phase voltage is applied to the sub electrode and the switching electrode so as to obtain darkness, and voltage with an opposite phase is applied to the sub electrode and the switching electrode so as to obtain brightness.
According to the above arrangement, the opposing electrode is grounded, in-phase voltage is applied to the sub electrode and the switching electrode so as to obtain darkness, and voltage with an opposite phase is applied to the sub electrode and the switching electrode so as to obtain brightness.
Besides, the following arrangement is also applicable: the opposing electrode has a predetermined and fixed potential, voltage with the same polarity, preferably voltage with the same voltage value is applied to the sub electrode and the switching electrode so as to obtain darkness, and voltage with opposite phase is applied to the sub electrode and the switching electrode so as to obtain brightness.
Therefore, when an image signal is applied via the switching element to the electrode (switching electrode) connected to the switching element, the switching electrode has a predetermined potential. In this case, a direction of an electric field, which is applied to liquid crystal, is varied between parallel and perpendicular to the substrate, depending upon whether a potential of the switching electrode is in phase or in opposite phase with a potential of the electrode (sub electrode), which is not connected to the switching electrode. Thus, the orientation of liquid crystal varies between horizontal orientation and vertical orientation. Consequently, the orientation of liquid crystal is varied by changing a potential phase of the switching electrode.
Thus, fast response can be achieved without a blurred moving image. Further, monochrome display is available with a remarkably preferable contrast. Also, with the combination of a color filter and so on, favorable full-color display is also available.
Additionally, the present invention does not need to form a resistant thin film, which is difficult to evenly form because of its small thickness. Hence, it is possible to prevent uneven display.
Moreover, the present invention requires only a single element for switching. Thus, it is possible to suppress an increase in manufacturing cost.
Besides, nematic liquid crystal is applicable to the present invention. Namely, without the necessity for ferroelectric liquid crystal, which achieves fast response but causes a peculiar problem such as uneven orientation, low resistance to impact, and burn, it is possible to achieve fast response by using nematic liquid crystal, which has been widely used, relatively easy to handle, and less prone to the above problems. For this reason, problems of even orientation, resistance to impact, and burn do not occur. Consequently, nematic liquid crystal can be used to provide a liquid crystal display device making high-speed electric field response at optical rising and falling.
Besides, the liquid crystal display device of the present invention, in which liquid crystal is formed in a gap between a pair of substrates including at least a single light-transmitting substrate, the device having a construction in which an electrode is formed on the substrate to apply a signal waveform electric field from outside to the liquid crystal, the liquid crystal changes its orientation according to an applied signal waveform, emitted light is modulated, and the modulation is visualized, is characterized in that a first substrate of a pair of the substrates includes a switching element, a resistant film, a switching electrode connected to the switching element and an electrode which is not connected to the switching element on the resistant film, and a second substrate includes an opposing electrode which is not connected to the switching element.
According to the above arrangement, the first substrate of the paired substrates includes the switching element, the resistant film, the switching electrode connected to the switching element and the electrode which is not connected to the switching element on the resistant film, and the second substrate includes the opposing electrode which is not connected to the switching element.
Further, the following arrangement is also applicable: a first substrate of the paired substrates includes a resistant film, a switching electrode where an image signal is applied on the resistant film, and a sub electrode acting as a non-switching electrode where an image signal is not applied on the resistant film, and a second substrate opposing the first substrate includes an opposing electrode where an image signal is not applied.
Therefore, when an image signal is applied via the switching element to the electrode (switching electrode) connected to the switching element, the switching electrode has a predetermined potential. In this case, a direction of an electric field, which is applied to liquid crystal, is varied between parallel and perpendicular to the substrate, depending upon whether a potential of the switching electrode is in phase or in opposite phase with a potential of the electrode (sub electrode), which is not connected to the switching electrode on the first substrate. Thus, the orientation of liquid crystal varies between horizontal orientation and vertical orientation. Consequently, the orientation of liquid crystal is varied by changing a potential phase of the switching electrode.
As a result, rising response and falling response can be controlled by an electric field. A reduction in viscosity causes no falling response, so that fast response can be achieved.
Therefore, fast response is available without a blurred moving image.
Moreover, the present invention requires only a single element for switching. Thus, it is possible to suppress an increase in manufacturing cost.
Further, the present invention does not need to form a resistant thin film, which is difficult to evenly form because of its small thickness. Hence, it is possible to prevent uneven display.
Besides, nematic liquid crystal is applicable to the present invention. Namely, without the necessity for ferroelectric liquid crystal, which achieves fast response but causes a peculiar problem such as uneven orientation, low resistance to impact, and burn, it is possible to achieve fast response by using nematic liquid crystal, which has been widely used, relatively easy to handle, and less prone to the above problems. For this reason, problems of even orientation, resistance to impact, and burn do not occur. Consequently, with nematic liquid crystal, it is possible to provide a liquid crystal display device making high-speed electric field response at optical rising and falling.
Furthermore, the displaying method of the present invention is characterized in that: in the liquid crystal display device having the above construction, signal waveforms with opposite polarities are applied to the electrode which is connected to the switching element and to the electrode which is not connected thereto on the first substrate, so that an electric field is generated in a substantially horizontal direction to a surface of the substrate between the electrode which is connected to the switching element and the electrode which is not connected thereto; and signal waveforms with the same polarities are applied to the electrode which is connected to the switching element and the electrode which is not connected to the switching element on the first substrate, so that an electric field is generated vertically to a surface of the substrate between the electrode which is connected to the switching element, the electrode which is not connected to the switching element, and the resistant film, and the grounded opposing electrode.
According to this arrangement, signal waveforms with opposite polarities are applied to the electrode which is connected to the switching element and the electrode which is not connected thereto on the first substrate, so that an electric field is generated in a substantially horizontal direction to a surface of the substrate between the electrode which is connected to the switching element and the electrode which is not connected thereto, and signal waveforms with the same polarities are applied to the electrode which is connected to the switching element and the electrode which is not connected thereto on the first substrate, so that an electric field is generated vertically to a surface of the substrate between the electrode which is connected to the switching element, the electrode which is not connected to the switching element, and the resistant film, and the grounded opposing electrode.
Additionally, the following arrangement is also applicable: on the first substrate, signal waveforms with opposite polarities are applied to the switching electrode where an image signal is applied and the sub electrode where an image signal is not applied, so that an electric field is generated in a substantially horizontal direction to a surface of the substrate between the switching electrode and the sub electrode; meanwhile, signal waveforms with the same polarity are applied to the switching electrode and the sub electrode, so that an electric field is generated vertically to the surface of the substrate between the switching electrode, the sub electrode, and the resistant film, and the opposing film.
Therefore, when an image signal is applied via the switching element to the electrode (switching electrode) connected to the switching element, the switching electrode has a predetermined potential. In this case, a direction of an electric field, which is applied to liquid crystal, is varied between parallel and perpendicular to the substrate, depending upon whether a potential of the switching electrode is in phase or in opposite phase with a potential of the electrode (sub electrode), which is not connected to the switching electrode on the first substrate. Thus, the orientation of liquid crystal varies between horizontal orientation and vertical orientation. Consequently, the orientation of liquid crystal is varied by changing a potential phase of the switching electrode.
As a result, rising response and falling response can be controlled by an electric field. A reduction in viscosity causes no falling response, so that fast response can be achieved.
Therefore, fast response is available without a blurred moving image.
Moreover, the present invention requires only a single element for switching. Thus, it is possible to suppress an increase in manufacturing cost.
Further, the present invention does not need to form a resistant thin film, which is difficult to evenly form because of its small thickness. Hence, it is possible to prevent uneven display.
Besides, nematic liquid crystal is applicable to the present invention. Namely, without the necessity for ferroelectric liquid crystal, which achieves fast response but causes a peculiar problem such as uneven orientation, low resistance to impact, and burn, it is possible to achieve fast response by using nematic liquid crystal, which has been widely used, relatively easy to handle, and less prone to the above problems. For this reason, problems of even orientation, resistance to impact, and burn do not occur. Consequently, with nematic liquid crystal, it is possible to provide a liquid crystal display device making high-speed electric field response at optical rising and falling.
Moreover, the displaying method of the present invention is characterized in that the liquid crystal display device having the above construction includes a pair of polarizers, signal waveforms with opposite polarities are applied to the electrode which is connected to the switching element and the electrode which is not connected thereto on the first substrate, so that an electric field is generated in a substantially horizontal direction to a surface of the substrate, between the electrode which is connected to the switching element and the electrode which is not connected thereto, so as to provide bright display; and signal waveforms with the same polarity are applied to the electrode which is connected to the switching element and the electrode which is not connected to the switching element on the first substrate, so that an electric field is generated vertically to a surface of the substrate between the electrode which is connected to the switching element, the electrode which is not connected to the switching element, and the resistant film, and the grounded opposing electrode, so as to provide dark display.
According to the above arrangement, a pair of polarizers are provided, and signal waveforms with opposite polarities are respectively applied to the electrode which is connected to the switching element and the electrode which is not connected to the switching element on the first substrate, so that an electric field is generated in a substantially horizontal direction to a surface of the substrate, between the electrode which is connected to the switching element and the electrode which is not connected thereto, so as to provide bright display; and signal waveforms with the same polarity are applied to the electrode which is connected to the switching element and the electrode which is not connected to the switching element on the first substrate, so that an electric field is generated vertically to a surface of the substrate between the electrode which is connected to the switching element, the electrode which is not connected to the switching element, and the resistant film, and the grounded opposing electrode, so as to provide dark display.
Additionally, the following arrangement is also applicable: the opposing electrode has a fixed and predetermined potential, and signal waveforms with opposite polarities are applied to the electrode (switching electrode) where an image signal is applied and the electrode (sub electrode) where an image signal is not applied on the first substrate, so that an electric field is generated in a substantially horizontal direction to a surface of the substrate between the switching electrode and the sub electrode, so as to provide bright display; and signal waveform with the same polarity, preferably signal waveforms with the same voltage value are applied to the switching electrode and the sub electrode, so that an electric field is generated vertically to a surface of the substrate between the switching electrode, the sub electrode, and the resistant film, and the opposing electrode, so as to provide dark display.
Therefore, when an image signal is applied via the switching element to the electrode (switching electrode) connected to the switching element, the switching electrode has a predetermined potential. In this case, a direction of an electric field, which is applied to liquid crystal, is varied between parallel and perpendicular to the substrate, depending upon whether a potential of the switching electrode is in phase or in opposite phase with a potential of the electrode (sub electrode), which is not connected to the switching electrode on the first substrate. Thus, the orientation of liquid crystal varies between horizontal orientation and vertical orientation. Consequently, the orientation of liquid crystal is varied by changing a potential phase of the switching electrode.
Thus, fast response can be achieved without a blurred moving image. Further, monochrome display is available with a remarkably preferable contrast. Also, with the combination of a color filter and so on, favorable full-color display is also available.
Moreover, the present invention requires only a single element for switching. Thus, it is possible to suppress an increase in manufacturing cost.
Further, the present invention does not need to form a resistant thin film, which is difficult to evenly form because of its small thickness. Hence, it is possible to prevent uneven display.
Besides, nematic liquid crystal is applicable to the present invention. Namely, without the necessity for ferroelectric liquid crystal, which achieves fast response but causes a peculiar problem such as uneven orientation, low resistance to impact, and burn, it is possible to achieve fast response by using nematic liquid crystal, which has been widely used, relatively easy to handle, and less prone to the above problems. For this reason, problems of even orientation, resistance to impact, and burn do not occur. Consequently, nematic liquid crystal can be used to provide a liquid crystal display device making high-speed electric field response at optical rising and falling.
Besides, the liquid crystal display device of the present invention, in which liquid crystal is formed in a gap between a pair of substrates including at least a single light-transmitting substrate, the device having a construction in which an electrode is formed on the substrate to apply a signal waveform electric field from outside to the liquid crystal, the liquid crystal changes its orientation according to an applied signal waveform, emitted light is modulated, and the modulation is visualized, is characterized in that a first substrate of the paired substrates includes a first electrode and a second electrode which are respectively connected to a first switching element and a second switching element, a third electrode which is not connected to the switching element, and an insulator, the first electrode and the third electrode are opposed to the second electrode via the insulation film, and the second substrate includes an opposing electrode which is not connected to the switching element.
According to the above arrangement, the first substrate of the paired substrates includes the first electrode and the second electrode which are respectively connected to the first and second switching elements, the third electrode which is not connected to the switching element, and the insulator; the first electrode and the third electrode are opposed to the second electrode via the insulation film; and the second substrate includes the opposing electrode which is not connected to the switching element.
Further, the following arrangement is applicable: a first substrate of the paired substrates includes a second switching electrode film where an image signal is applied, an insulation film on the second switching electrode film, a first switching electrode where an image signal is applied and a sub electrode (third electrode) acting as a non-switching electrode where an image signal is not applied, on the insulation film, and a second substrate opposing the first substrate includes an opposing electrode where an image signal is not applied.
Therefore, when an image signal is applied to the electrodes (first and second switching electrodes) respectively connected to the first and second switching elements via the switching elements, the first and second switching electrodes have predetermined potentials. In this case, a direction of an electric field, which is applied to liquid crystal, is varied between parallel and perpendicular to the substrate, depending upon whether potentials of the first and second switching electrodes are in phase or in opposite phase with potentials of the electrodes (sub electrode, third electrode), which are not connected to the switching electrode on the first substrate. Thus, the orientation of liquid crystal varies between horizontal orientation and vertical orientation. Consequently, the orientation of liquid crystal is varied by changing a potential phase of the switching electrode.
Consequently, rising response and falling response can be controlled by an electric field. A reduction in viscosity causes no falling response, so that fast response can be achieved.
Therefore, fast response is available without a blurred moving image.
Further, the present invention does not need to form a resistant thin film, which is difficult to evenly form because of its small thickness. Hence, it is possible to prevent uneven display.
Besides, nematic liquid crystal is applicable to the present invention. Namely, without the necessity for ferroelectric liquid crystal, which achieves fast response but causes a peculiar problem such as uneven orientation, low resistance to impact, and burn, it is possible to achieve fast response by using nematic liquid crystal, which has been widely used, relatively easy to handle, and less prone to the above problems. For this reason, problems of even orientation, resistance to impact, and burn do not occur. Consequently, with nematic liquid crystal, it is possible to provide a liquid crystal display device making high-speed electric field response at optical rising and falling.
Furthermore, the displaying method of the liquid crystal display device according to the present invention is characterized in that: in the liquid crystal display device having the above arrangement, signal waveforms with opposite polarity are applied to the first electrode and the third electrode, so that an electric field is generated in a substantially horizontal direction to a surface of the substrate between the first and the third substrates; and signal waveforms with the same polarity are applied to the first to third electrodes, so that an electric field is generated vertically to a surface of the substrate between the first to third electrodes and the opposing electrode on the second substrate.
According to the above arrangement, signal waveforms with opposite polarity are applied to the first electrode and the third electrode, so that an electric field is generated in a substantially horizontal direction to a surface of the substrate between the first and the third substrates; and signal waveforms with the same polarity are applied to the first to third electrodes, so that an electric field is generated vertically to a surface of the substrate between the first to third electrodes and the opposing electrode on the second substrate.
Also, the following arrangement is also applicable: the opposing electrode and the second electrode have predetermined and fixed potentials, signal waveforms with opposite polarity are applied to the first electrode (switching electrode) where an image signal is applied and the third electrode (sub electrode) where an image signal is not applied on the first substrate, so that an electric field is generated in a substantially horizontal direction to a surface of the substrate between the switching electrode and the sub electrode so as to provide bright display; and signal waveforms with the same polarity, preferably with the same voltage value are applied to the switching electrode, the sub electrode and the second electrode, so that an electric field is generated vertically to a surface of the substrate between the switching electrode, the sub electrode, and the second electrode, and the opposing electrode so as to provide dark display.
Therefore, when an image signal is applied via the switching element to the electrodes (first and second switching electrodes) respectively connected to the first and second switching elements, the first and second switching electrodes respectively have predetermined potentials. In this case, a direction of an electric field, which is applied to liquid crystal, is varied between parallel and perpendicular to the substrate, depending upon whether potentials of the first and second switching electrodes are in phase or in opposite phase with potentials of the electrodes (sub electrode, third electrode), which are not connected to the switching electrode on the first substrate. Thus, the orientation of liquid crystal varies between horizontal orientation and vertical orientation. Consequently, the orientation of liquid crystal is varied by changing a potential phase of the switching electrode.
Thus, fast response can be achieved without a blurred moving image. Further, monochrome display is available with a remarkably preferable contrast. Also, with the combination of a color filter and so on, favorable full-color display is also available.
Further, the present invention does not need to form a resistant thin film, which is difficult to evenly form because of its small thickness. Hence, it is possible to prevent uneven display.
Besides, nematic liquid crystal is applicable to the present invention. Namely, without the necessity for ferroelectric liquid crystal, which achieves fast response but causes a peculiar problem such as uneven orientation, low resistance to impact, and burn, it is possible to achieve fast response by using nematic liquid crystal, which has been widely used, relatively easy to handle, and less prone to the above problems. For this reason, problems of even orientation, resistance to impact, and burn do not occur. Consequently, with nematic liquid crystal, it is possible to provide a liquid crystal display device making high-speed electric field response at optical rising and falling.
For a fuller understanding of the nature and advantages of the invention, reference should be made to the ensuing detailed description taken in conjunction with the accompanying drawings.